1. Field of the Invention
The present invention relates generally to a backlight for a liquid crystal display television and, more particularly, to a liquid crystal display array module for providing backlight, which can be used as an independent device with a plurality of light emitting diodes being integrally packaged, and which can be universally used regardless of a screen size, and a backlight unit having the same.
2. Description of the Related Art
Light Emitting Diodes (LEDs) are semiconductor light emitting devices that are light emitting sources formed through the modification of compound semiconductor materials, such as GaAs, AlGaAs, GaN, InGaN and AlGaInP, and generate light of various colors. Additionally, for the criteria of determining the characteristics of an LED device, there are a color, luminance and the intensity of light. Such characteristics of the LED device are determined first by a compound semiconductor material used in the LED device, and considerably affected second by the structure of a package for mounting an LED chip.
Especially, with the advent of high efficiency three primary color (red, blue and green) and white color LEDs implemented using GaN whose physical and chemical characteristics are excellent, the application of LEDs is extended to and used in various fields, such as the backlights of a keypad and a Liquid Crystal Display (LCD) device, a signal light, the guide light of an airport runway, and the reading lights and illumination lights of an airplane and an automobile having high directionality.
FIGS. 1a and 1b are a perspective view and a cross section showing an LED device 10 used as the light source of conventional backlight, respectively.
Referring to the drawings, the LED device 10 is formed in such a way that a frame 11 made of a plastic material is provided with leads 11a for inputting and outputting electric signals and a heat sink 12 made of a conductive material, an LED chip 14 is mounted on the heat sink 12, and a lens 16 constructed to reflect light generated from the LED chip 14 in a horizontal direction is combined with the upper portion of the frame 11.
A package structure formed of the frame 11 and the lens 16 is constructed to radiate light generated from the LED chip 14 in an almost horizontal direction and discharge heat generated from the LED chip 14 to the outside thereof, so that stable operating characteristics can be achieved.
FIG. 2 is a view showing a conventional backlight unit implemented using LED devices 10 having such horizontally emitting characteristics, and FIG. 3 is an enlarged view showing an LED array 21 included in the backlight unit of FIG. 2.
As shown in FIGS. 2 and 3, the conventional backlight unit 20 is packaged as shown in FIG. 1, and an LED array module 21 of the conventional backlight unit 20 is formed in such a way that a plurality of LED devices 10 each radiating one of red, blue and green light are mounted in a line to allow three primary colors to be alternately arranged on a Printed Circuit Board (PCB) 30 in which a printed circuit pattern for transmitting electric signals is formed. Additionally, the backlight unit 20 is divided into two equal parts, the LED array module 21 is arranged on the center portion of each divided part, and reflection plates 23 for reflecting horizontally radiated light in a vertical direction are formed on the both sides of the LED array module 21. The PCB 30 of the array module 21 is made of a highly conductive material, such as Al, to increase heat radiation efficiency.
The light radiated from the LED devices 10 that are mounted on the LED array modules 21 is refracted in a vertical direction and dispersed to an entire display screen.
The number of the array modules 21 required by the backlight unit 20 increases in proportion to the screen size of a corresponding display device, and the number of the LED devices 10 required by each LED array module 21 also varies with the screen size of the display device.
Accordingly, as described above, the conventional backlight unit is disadvantageous in that array modules 21 and reflectors 23 should be redesigned in accordance with the screen size of a display device, and the number of high priced-LED devices 10 is increased in proportion to the screen size of the display device.
Furthermore, since the conventional backlight unit causes array modules to be arranged in parallel, the conventional backlight unit is problematic in that the luminance characteristics of the edge portions of the backlight unit spaced apart from the array module 21 are relatively deteriorated compared to those of the center portion thereof.
Furthermore, since the LED array module is constructed to be a single unit, the conventional backlight unit is problematic in that the entire LED array module must be inspected for a defect in the case where the defect occurs in a portion thereof.